1. Field of the Invention
The present invention pertains to an aerobically curing composition, the preparation thereof and use thereof.
2. Discussion of Related Art
Bonded joints can be found in household utensil, electrical, electronics, furniture, sports article, construction (indoor and outdoor), ceramics industries and in automobile manufacture including their subcontractors. The machine-building trade benefits from adhesive properties as well as mountings or installation technologies where sealing functions must also be served. In addition to combinations of similar materials, such as steel, aluminum, brass, copper, painted metallic surfaces, wood, glass, PVC, PC (polycarbonate), and ABS, pairs of different materials are particularly important in terms of adhesive properties. In such composite bondings, the limit of the performance of known adhesive systems is frequently reached due to different thermal expansion behaviors or adhesion loss, also with materials such as ferrite or ceramics. In some applications, the adhesives must have additional damping properties or must not have corrosion-promoting properties at different electrochemical potentials.
Limits of application are known for the known adhesive systems, such as two-component epoxy resins, cyanoacrylates, dispersion, contact, two-component acrylate, two-component polyurethane or anaerobically curing adhesives, with respect to gap-filling performance, elasticity, automatical metering, heat resistance, volatility and ageing properties.
Further, short cycle times are predominantly required for bondings of a variety of materials in industrial automated production. Many adhesive formulations require waiting times for the activation of the adhesive (prior to and after joining) which cannot be accepted in industrial automated production.
Further, metering and storing of the adhesives is very important. According to the prior art, a flexible plastic container is filled with an adhesive or sealant (e.g. anaerobic adhesive) and inserted into a compressed-air vessel comprising a fixture. Extraction of the containers, in which an ascending pipe has been inserted, is performed by admitting compressed air in the compressed-air vessel. By means of a hose pipe, the product is brought to the corresponding site of application and metered with a metering valve. By this method, the containers cannot be discharged to less than 10% of residual contents. Also, with anaerobic adhesives, the additional uptake of compressed air by the product has a disadvantageous effect on metering. For metering aerobic adhesives, there have been no possibilities of automatic metering from tubes and flexible plastic containers to date.
In order to shorten the period between the application of the adhesive and the joining of the parts to be connected, the oxygen can be added to the adhesive already prior to its application. This requires the inclusion of a mixing chamber in which the oxygen, whether in pure form or in the form of air, is added to the adhesive with more or less pressure. This mixing chamber should be positioned between the product outlet and the distributing valve. Preferably it is incorporated in the distributing valve. Also, it is advantageous for the mixing chamber to be heatable such that the time of air contact can be adapted to the respective bonding process. Thus, it is possible to adjust the duration of the bonding process to the cycle times of a series production.
Therefore, it is the object of the present invention to provide a one-component, aerobically curing adhesive composition which rapidly forms a high-strength polymer resistant to heat, ageing and moisture and which is useful for bonding a wide variety of similar materials and different materials (composites).
Further, the composition should be apt to be used in a special process in which the air-contacting periods for the activation of the adhesive are still shortened so that it can also be used in industrial production involving shorter cycle times.
In addition, it has been another object of the invention to provide a system for storing and metering the aerobic adhesive according to the invention.
The first object has been achieved, according to the invention, by an aerobically curing composition comprising free-radical polymerizable compounds, an activator system, and optionally conventional additives, characterized in that said composition contains as said free-radical polymerizable compounds
A) at least one polyurethane (meth)acrylate of the general formula: EQU [H.sub.2 C.dbd.CR.sup.1 --C(.dbd.O)--O---R.sup.2 --O--C(.dbd.O)--NH--].sub.n R.sup.3 (I) PA1 R.sup.1 is hydrogen or a methyl group; PA1 R.sup.2 is a linear or branched chain alkyl group containing from PA1 2 to 6 carbon atoms or alkylene oxide containing from 4 to PA1 21 carbon atoms; PA1 n is 2 or 3; and PA1 R.sup.3, for n=2, is: EQU [--Q--NH--C(.dbd.O)].sub.2 [{--O--R.sup.4 --O--C(.dbd.O)--NH--Q'--NH--C(.dbd.O)}.sub.m --O--R.sup.4 --O--] PA1 R.sup.4 is PA1 a) a polycaprolactonediol residue; PA1 c) a diol residue derived from a polyesterdiol which is characterized by a C:O ratio of &gt;2.6, a C:H ratio of &lt;10, and a molecular weight of from 1000 to 20,000; or PA1 R.sup.3, for n=3, is: EQU [Q--NH--C(.dbd.O)--O--((CH.sub.2).sub.5 --C(.dbd.O)).sub.p --].sub.3 R.sup. 5 PA1 Q and Q' independently are aromatic, aliphatic or cycloaliphatic groups containing from 6 to 18 carbon atoms which are derived from diisocyanates or diisocyanate mixtures; and PA1 B) one or more (meth)acrylate comonomers;
wherein
wherein m is from 0 to 10;
b) a polytetrahydrofurfuryldiol residue;
d) a dial residue derived from a PES dial which is liquid at 20.degree. C. and has a molecular weight of from 4000 to 10,000 by HPRC; and
wherein R.sup.5 is a trial residue of a linear or branched chain trihydric alcohol containing from 3 to 6 carbon atoms, and p is from 1 to 10; and
wherein said composition contains from 20 to 80% by weight of said polyurethane (meth)acrylate and from 80 to 20% by weight of said (meth)acrylate comonomer(s), based on the total of polymerizable compounds, and said activator system is a hydrazone activator system.